Lunt calcium filter imaging thread

this is the main message area for anything solar :)
User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Lunt calcium filter imaging thread

Post by TheSkyBurner » Fri Sep 28, 2018 4:25 am

Hello all,

I would like to start a thread dedicated to users imaging with the Lunt series calcium filters.

Please post any images you have here, no equipment photos please! Just solar images. Processed, unprocessed, good , bad hih res, low res. It does not matter.

I need data to compare with.

Please do not post modified coronado pst images here. This is not a marketed device and there is no way for anybody to purchase one.

Thanks to anybody that participate’s!

User avatar
Montana
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 19657
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK

Re: Lunt calcium filter imaging thread

Post by Montana » Fri Sep 28, 2018 7:02 am

This is my best
Image220516_081515 by Alexandra Hart, on Flickr

But mostly like this
Image 180617_073020 by Alexandra Hart, on Flickr

These are the best, 99% I through away as they are blurred after processing.

Alexandra

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2989
Joined: Sun Nov 18, 2012 3:13 pm

Re: Lunt calcium filter imaging thread

Post by Valery » Fri Sep 28, 2018 8:37 am

Apollo,

Lunt CaK is 2,4A and the PST is 2.2A. I have compared the Lunt CaK 12mm diagonal and my PST CaK in the configuration I have now.
Lunt was better than PST CaK if the PST CaK was single stacked. I belive this was because the blocking filter of the PST was rusty. I stick with the PST hoping to change the bloking filter for baader K-line. This was not realized yet.

As far as I know, the PST CaK is 3 or 4 cavity filter. It works very good from F/7 to F/40 without noticeable degradation at F/7.
Same with the Lunt CaK filter.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

christian viladrich
Im an EXPERT!
Im an EXPERT!
Posts: 424
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Contact:

Re: Lunt calcium filter imaging thread

Post by christian viladrich » Fri Sep 28, 2018 3:19 pm

Here is an image taken a while ago with the Lunt Ca K filter:
Image

This is quite a good Ca K filter. I use it with a 150 mm refractor and no ERF with no problem. But don't use it with a larger aperture and no ERF. A friend tested it with a 200 mm and the fiter got damaged ...
Christian Viladrich
Co-author of "Astronomie Planétaire"
http://www.astroplanetes.com/
Co-author of "Astronomie Solaire"
http://www.astronomiesolaire.com/

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2989
Joined: Sun Nov 18, 2012 3:13 pm

Re: Lunt calcium filter imaging thread

Post by Valery » Fri Sep 28, 2018 4:37 pm

christian viladrich wrote:
Fri Sep 28, 2018 3:19 pm
Here is an image taken a while ago with the Lunt Ca K filter:
Image

This is quite a good Ca K filter. I use it with a 150 mm refractor and no ERF with no problem. But don't use it with a larger aperture and no ERF. A friend tested it with a 200 mm and the fiter got damaged ...
Christian,

Thanks for the input.

BTW Did you ever perform the direct comparision of your Barr CaK and Lunt CaK filters?


Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
marktownley
Librarian
Librarian
Posts: 24357
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Lunt calcium filter imaging thread

Post by marktownley » Fri Sep 28, 2018 5:50 pm

Spherical aberration is the key hindrance at these wavelengths.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

christian viladrich
Im an EXPERT!
Im an EXPERT!
Posts: 424
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Contact:

Re: Lunt calcium filter imaging thread

Post by christian viladrich » Fri Sep 28, 2018 6:17 pm

I also found out that old one taken with the Lunt CaK :
Image

Valery, you made me check my data log :-)
In fact, I broke my Baader K-line filter (which I used at that time as an ERF for the Barr Ca K filter) when I had the Lunt Ca K for testing. So I have no direct comparison.

This being said, the difference between the Baar filter and the Lunt is clear when you compare the image I took with the Lunt on August 17 (in my previous message above) and the image taken one day earlier with the Barr filter :
Image

Another point of interest is that the images with the Lunt and the Barr filters are taken with the some exposure time, while the image scale of the image with the Baar is much larger. This means that the transmission of the Barr filter is higher that the transmission of the Lunt.
Christian Viladrich
Co-author of "Astronomie Planétaire"
http://www.astroplanetes.com/
Co-author of "Astronomie Solaire"
http://www.astronomiesolaire.com/

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Fri Sep 28, 2018 8:21 pm

christian viladrich wrote:
Fri Sep 28, 2018 3:19 pm
Here is an image taken a while ago with the Lunt Ca K filter:
Image

This is quite a good Ca K filter. I use it with a 150 mm refractor and no ERF with no problem. But don't use it with a larger aperture and no ERF. A friend tested it with a 200 mm and the fiter got damaged ...
Do you have any unprocessed data left? The sharpness is a personal touch, and is unique to your work flow.

Alexandra, thats what im looking for! Phenomenal. perfect processing. Unfortunately i wont have any sunspots, but your surrounding chromosphere is where my focus is. You just set a massive hurdle for me, gonna need to get a powermate to match thus scale.

Valery: i have tried using the baader filter unsuccessfully. It always procured a double image overlapping the surface no matter how much i tilted it. The distance between the two glass elements is like 1.5mm, not far enough to work with high intensity light.. You may have better results, but if you are going to get it you really need to consider removing the top element and seperating it from the tilted element. Place them individually in Their own cell.

I still want to mail you a skybender if you can give me a shipping address!

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Fri Sep 28, 2018 8:35 pm

marktownley wrote:
Fri Sep 28, 2018 5:50 pm
Spherical aberration is the key hindrance at these wavelengths.

I have a safix i could throw in my optics, but that is cheating :)

Not everyone can get that anymore, sure a couple float around used but i prefer to share unadulterated images that everyone can expect to achieve.

I do have a 30year old c8 sct. But i dont have a collimator , and it could be one of those bad ones which can never be fixed. I put bobs knobs on it, but at the same time dont have the patience to use a star. I can never get stable tracking on anything.

I attempted to use my neighbors lamp, but that doesnt work for diffraction rings. Also just carrying the scopes outside knock them out of whack!

User avatar
p_zetner
Almost There...
Almost There...
Posts: 893
Joined: Sun Mar 18, 2012 4:59 pm
Location: Winnipeg, Manitoba, Canada

Re: Lunt calcium filter imaging thread

Post by p_zetner » Fri Sep 28, 2018 11:40 pm

Here are older images taken of the full disk, an AR closeup and proms (with inverted disk). All were taken with Lunt B1800. All except the full disk had the Lunt stacked with an Omega 2 Angstrom (nominally) filter. Possibly a contrast improvement ... not sure and didn't really carry out study with / without the Omega.

Cheers.
Peter
full disk labels siz.png
full disk labels siz.png (2.27 MiB) Viewed 421 times
AR closeup labels siz.png
AR closeup labels siz.png (2.95 MiB) Viewed 421 times
prom inv disk labels siz.png
prom inv disk labels siz.png (2.41 MiB) Viewed 421 times

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sat Sep 29, 2018 1:57 am

Wow peter, those last two images are phenomenal. I wonder if the pgr is working some of the superiority here? Ill have to look at the icx694 specsheet and compare it to my basler 1300-30

I have some hard work ahead of me now after alexandra’s and your post.

Got any unprocessed images by any chance?
(Ooooff thats one pricey chip)

(edit) oh i see what I over looked here. Peter has got an apo-triplet. that explains it! Super-apo telescopes are just in a league of their own for all wavelengths. I cant beat that high strehl ratio with out using my 150mm f15....

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sat Sep 29, 2018 2:56 am

Okay thanks guys, i have what i need.

Now back to work, i will share my results when complete.

christian viladrich
Im an EXPERT!
Im an EXPERT!
Posts: 424
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Contact:

Re: Lunt calcium filter imaging thread

Post by christian viladrich » Sat Sep 29, 2018 8:10 am

BTW, in adddition to the Lunt, the Daystar Ca H filter is another good Ca K filter.
Christian Viladrich
Co-author of "Astronomie Planétaire"
http://www.astroplanetes.com/
Co-author of "Astronomie Solaire"
http://www.astronomiesolaire.com/

User avatar
marktownley
Librarian
Librarian
Posts: 24357
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Lunt calcium filter imaging thread

Post by marktownley » Sat Sep 29, 2018 8:18 am

TheSkyBurner wrote:
Sat Sep 29, 2018 1:57 am
Peter has got an apo-triplet. that explains it! Super-apo telescopes are just in a league of their own for all wavelengths. I cant beat that high strehl ratio with out using my 150mm f15....
At 393 it's not about strehl it's about spherical aberration. That 115/7 (along with the TOAs) have very little SA down in the blue. High strehl is definitely not a indicator a scope will perform well deep down in the blue.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

christian viladrich
Im an EXPERT!
Im an EXPERT!
Posts: 424
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Contact:

Re: Lunt calcium filter imaging thread

Post by christian viladrich » Sat Sep 29, 2018 9:11 am

Hello Mark,
If I may, I would suggest rephrasing your statement as follows :
"the Strelh ratio at 436 nm (g band for the opticians) is not relevant to the performance of the refractor at 393 nm".
This is because the spherical aberration increases very fast when you go to shorter wavelengths.

Here is an example with the SC :
Image
Because of the refractive index evolution with the wavelength, spherical aberration increases gently with longer wavelengths, and sharply will shorter wavelengthx.

Indeed, the Strehl ratio includes all aberrations of the optics. Accordingly, The Strelh ratio at 393 nm is fully relevant to the performance of the optic at 393 nm. The optics is diffraction limited when the Strelh is greater than 0.8.

Best regards
Christian Viladrich
Co-author of "Astronomie Planétaire"
http://www.astroplanetes.com/
Co-author of "Astronomie Solaire"
http://www.astronomiesolaire.com/

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2989
Joined: Sun Nov 18, 2012 3:13 pm

Re: Lunt calcium filter imaging thread

Post by Valery » Sat Sep 29, 2018 1:43 pm

This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
marktownley
Librarian
Librarian
Posts: 24357
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Lunt calcium filter imaging thread

Post by marktownley » Sat Sep 29, 2018 3:47 pm

christian viladrich wrote:
Sat Sep 29, 2018 9:11 am
Hello Mark,
If I may, I would suggest rephrasing your statement as follows :
"the Strelh ratio at 436 nm (g band for the opticians) is not relevant to the performance of the refractor at 393 nm".
This is because the spherical aberration increases very fast when you go to shorter wavelengths.

Here is an example with the SC :
Image
Because of the refractive index evolution with the wavelength, spherical aberration increases gently with longer wavelengths, and sharply will shorter wavelengthx.

Indeed, the Strehl ratio includes all aberrations of the optics. Accordingly, The Strelh ratio at 393 nm is fully relevant to the performance of the optic at 393 nm. The optics is diffraction limited when the Strelh is greater than 0.8.

Best regards
Fair point Christian, that says it better than I put it.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
marktownley
Librarian
Librarian
Posts: 24357
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Lunt calcium filter imaging thread

Post by marktownley » Sat Sep 29, 2018 5:28 pm

Valery wrote:
Sat Sep 29, 2018 1:43 pm
This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
Hi Valery,

Is the c11 one that you selected from a number over time, or this the only one you've had?

Mark
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2989
Joined: Sun Nov 18, 2012 3:13 pm

Re: Lunt calcium filter imaging thread

Post by Valery » Sat Sep 29, 2018 6:03 pm

marktownley wrote:
Sat Sep 29, 2018 5:28 pm
Valery wrote:
Sat Sep 29, 2018 1:43 pm
This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
Hi Valery,

Is the c11 one that you selected from a number over time, or this the only one you've had?

Mark
This is the very same C11 telescope I started the high res imaging with. It has very average optics. I'd better have
a telescope with somewhat smoother optics.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sat Sep 29, 2018 7:36 pm

Valery wrote:
Sat Sep 29, 2018 1:43 pm
This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
Valery: it is a good image, but it is not entirely "crisp". It is very blurry to my eyes, and it is over processed to bring out the details. Processing is a personal ability, and not a good indication of how well the scope is. It is a factor of lucky imaging.

You would get a better image if the optics were turned in favor of the blue wavelength, your hydrogen alpha image is the proof in the pudding. It is so much sharper, and has pure definition across all the whole-image. Which means the optics on the c11 are definitely made for h-alpha more than calcium. (as they should be, it is a deep space imaging scope)

If you could post the single frame data or a 10 frame raw data animation we can conclude the sharpness with better opinion of the sct optics. http://gifmaker.org/ (just extract 10 frames from the .avi file using avidub and upload them to gifmaker)

Post 10 frames of h-alpha raw, and 10 frames of calcium raw (unedited, unprocessed, screen grabbed straight from the .ser capture.)

Again, the image is great. But, there are definitely better optics out there for this color, like peters. We all work with what we have.


However I would trade the c11 for the apo triplet every day of the week,. (sacrificing the aperture for the strehl)

Valery: if i could give you my 150mm f/15 telescope, i would. You would likely use many times over the c11 and c14. Sometimes more aperture is not always the best choice, but of course; aperture IS king!


Christian your images are going to be very helpful! Thanks for posting. :band2

User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2989
Joined: Sun Nov 18, 2012 3:13 pm

Re: Lunt calcium filter imaging thread

Post by Valery » Sat Sep 29, 2018 7:41 pm

TheSkyBurner wrote:
Sat Sep 29, 2018 7:36 pm
Valery wrote:
Sat Sep 29, 2018 1:43 pm
This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
Valery: it is a good image, but it is not entirely "crisp". It is very blurry to my eyes, and it is over processed to bring out the details. Processing is a personal ability, and not a good indication of how well the scope is. It is a factor of lucky imaging.

You would get a better image if the optics were turned in favor of the blue wavelength, your hydrogen alpha image is the proof in the pudding. It is so much sharper, and has pure definition across all the whole-image. Which means the optics on the c11 are definitely made for h-alpha more than calcium. (as they should be, it is a deep space imaging scope)

If you could post the single frame data or a 10 frame raw data animation we can conclude the sharpness with better opinion of the sct optics. http://gifmaker.org/ (just extract 10 frames from the .avi file using avidub and upload them to gifmaker)

Post 10 frames of h-alpha raw, and 10 frames of calcium raw (unedited, unprocessed, screen grabbed straight from the .ser capture.)

Again, the image is great. But, there are definitely better optics out there for this color, like peters. We all work with what we have.


However I would trade the c11 for the apo triplet every day of the week,. (sacrificing the aperture for the strehl)

Valery: if i could give you my 150mm f/15 telescope, i would. You would likely use many times over the c11 and c14. Sometimes more aperture is not always the best choice, but of course; aperture IS king!


Christian your images are going to be very helpful! Thanks for posting. :band2
This image is nearly as 1,6x larger scale than the H-a image, Apollo. Resolution corresponds to 11" aperture at this wave length. High is not possible. Corrective optics has been used. Remember for the future: Valery is optical designer and systems and optics maker in a past and I know something in optics...
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sat Sep 29, 2018 9:02 pm

Valery wrote:
Sat Sep 29, 2018 7:41 pm
TheSkyBurner wrote:
Sat Sep 29, 2018 7:36 pm
Valery wrote:
Sat Sep 29, 2018 1:43 pm
This image is at 393nm continuum taken with a standard C11 280mm F/10 telescope.

download/file.php?id=34233

The image is quite crisp.
Valery: it is a good image, but it is not entirely "crisp". It is very blurry to my eyes, and it is over processed to bring out the details. Processing is a personal ability, and not a good indication of how well the scope is. It is a factor of lucky imaging.

You would get a better image if the optics were turned in favor of the blue wavelength, your hydrogen alpha image is the proof in the pudding. It is so much sharper, and has pure definition across all the whole-image. Which means the optics on the c11 are definitely made for h-alpha more than calcium. (as they should be, it is a deep space imaging scope)

If you could post the single frame data or a 10 frame raw data animation we can conclude the sharpness with better opinion of the sct optics. http://gifmaker.org/ (just extract 10 frames from the .avi file using avidub and upload them to gifmaker)

Post 10 frames of h-alpha raw, and 10 frames of calcium raw (unedited, unprocessed, screen grabbed straight from the .ser capture.)

Again, the image is great. But, there are definitely better optics out there for this color, like peters. We all work with what we have.


However I would trade the c11 for the apo triplet every day of the week,. (sacrificing the aperture for the strehl)

Valery: if i could give you my 150mm f/15 telescope, i would. You would likely use many times over the c11 and c14. Sometimes more aperture is not always the best choice, but of course; aperture IS king!


Christian your images are going to be very helpful! Thanks for posting. :band2
This image is nearly as 1,6x larger scale than the H-a image, Apollo. Resolution corresponds to 11" aperture at this wave length. High is not possible. Corrective optics has been used. Remember for the future: Valery is optical designer and systems and optics maker in a past and I know something in optics...
My eyes do not lie, you could know everything about optics and still post images with blurryness.

The h alpah i age is perfect. In every sense. The 393image is not. There is no argu8ng about how much knowledge you have. It is the obvious nature of the scope being used.

Knowledge means nothing compared to hands on experience! I am a highschool dropout, and i used trial and error to figure out everything i have. Smart people are equally capable as, Uneducated people. Some people are just more fortunate than others.(financially). Anybody can buy knowledge. Nobody can buy experience, that takes a solid effort.(you have both knowledge and experience). I am not arguing that either. Nor the high resolution you are using. 99of people here cant touch a 20meter resolution like you are using.


Post your unedited animated images, do not be afraid. Nobody is going to judge you. You are an amazing solar imager! One of the best.

We would like to see the actual frames you are working with, not what you fixed about them

Teamwork valery.... teamwork.

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sat Sep 29, 2018 10:00 pm

Valery wrote:
Sat Sep 29, 2018 7:41 pm

Remember for the future: Valery is optical designer and systems and optics maker in a past and I know something in optics...
Valery,. along time ago you once told me that a lens I was using would do nothing for my system because it was not designed for it. Well, i used this very same lens to achieve my new results which are far superior to what I WAS getting.

Am I an optical designer, past and future? I also designed and built a system, with my own methodology.....
I do things the way I am because I refuse to believe something without using my own hands and eyes.

You may be using corrective optics, but like mine, it is entirely possible one of the lenses is just 10mm off.

I am here, looking for teamwork and other users data because I am designing a system that belongs to an entire world network. Not just one guy, alone in his backyard.

original post here
https://www.cloudynights.com/topic/4627 ... onado-cak/
negative infrared.png
negative infrared.png (64.31 KiB) Viewed 265 times

Now this is very good for an optic that was not intended to be there..... (can it be better? Of course.. but like I said i do things with my hands and eyes. Not a piece of paper or software.) Does it look soft? Does it look like there is coma? NO! So are you still so sure of your high confidence?

I didnt use a single piece of paper or a single ruler to invent my Skybender. Now its literally used world wide.
(again, I am a high school drop out. I am quite proud of it as well; I take care of four kids and still invent new products.)



BEFORE
Image
AFTER
Image

TEAM WORK IS ESSENTIAL. Can we help each other? YES WE CAN.

Now here, when comparing my latest images with TWO university grade spectrohelioscope's (which is by all means developed by actual people with degrees in optics; i can then argue all day long about the progress I am making is indeed carved in a positive direction regardless of my "incorrect" optics, lack of education, and "undeveloped" knowledge....

I did not use any image editing, nor lucky imaging. This is all raw, single frame "dirty" data.

Image
Image credit Paris Meudon observatory
---------------------------------------------
Image
Image credit University of Coimbra

User avatar
marktownley
Librarian
Librarian
Posts: 24357
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: Lunt calcium filter imaging thread

Post by marktownley » Sun Sep 30, 2018 11:45 am

I thought this scope was a good example of how strehl varies with wavelength - the apm 152/7.8 doublet https://www.apm-telescopes.de/en/telesc ... 9-ota.html At either end of the spectrum the strehl plummets away :o
Strehlkurve.jpg
Strehlkurve.jpg (133.05 KiB) Viewed 212 times
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
TheSkyBurner
Almost There...
Almost There...
Posts: 607
Joined: Sat May 05, 2018 7:55 pm
Contact:

Re: Lunt calcium filter imaging thread

Post by TheSkyBurner » Sun Sep 30, 2018 4:20 pm

marktownley wrote:
Sun Sep 30, 2018 11:45 am
I thought this scope was a good example of how strehl varies with wavelength - the apm 152/7.8 doublet https://www.apm-telescopes.de/en/telesc ... 9-ota.html At either end of the spectrum the strehl plummets away :o

Strehlkurve.jpg
There are some chinese made 102mm x 1200mm objectives on ebay. I am strongly considering to test it.

It seems really cheap optics perform rather good, because if a optic is corrected for performance it tends to remove the blue frige in favor of green light.

I want blue fringe / purpl fringe optics for a dedicated scope. I am going to be trying the meade etx80 and get it proper for the all day robot tracking.. set it and forget it type imaging.

Post Reply

Who is online

Users browsing this forum: No registered users and 6 guests